Electrical heating unit



March 4, 1930. c. w. LOGAN ELECTRICAL HEATING UNIT Filed Deo. 29, 192B gjm/verde@ Patented Mar. 4, 1930 UNITED STATES i PATENT OFFICE CHARLES W. LOGAN, OF KENMORE, NEW YORK, ASSIGNOR TO MAR-KIEL ELECTRIC PRODUCTS, INC., OF BUFFALO, NEW YORK, A CORPORATION 0F NEW YORK ELECTRICAL HEATING UNIT Application filed December 29, 1928.

This invention relates to improvements in electrical heating units, particularly of the general type which includes a heating element of coiled resistance wire and a refrac- 5 tory support ordinarily formed with grooves in which the heating element is placed.

In providing terminal connections for units of this type, the usual practice has been to utilize bolt and nut fastenings, the bolts extending through openings in the refractory support and forming parts of the current path. Owing to the expansion and contraction of the support during the use of the unit, there is a marked tendency for the elements of the bolt and nut fastenings to work loose with consequent heating and arcing at the points of connection of the lead-in wires and for the heating element. Furthermore, the movement of the bolt and connected parts together with the heating and arcing of the connections will, in time, cause such parts as the heating element and lead-in wires, to break off.

The principal object of the invention is to provide a construction in which the terminal connections are absolutely unaffected by the expansion and contraction of the support.

An embodiment of the invention is illustrated in the accompanying drawings, Wherein:

Figure l is a top plan view of the heating unit.

Figure 2 is a section along line 2-2 of Figure 1.

The support of the unit which is indicated at l may be made in any suitable form and composed of any suitable refractory material such as porcelain. The heating element indicatedvat 2 is arranged upon and secured to the support l in any desired manner. Preferably, however, the element 2 is arranged in a continuous groove 3 formed in the support and retained therein by cross members 4 which extend transversely over the groove at suitable points along its length.

The terminal connections for the element are positioned in the opposite end of the groove 3 which for convenience are arranged in mutual adjacency. Each terminal connec tion includes a metal strap 5 which is laid Serial No. 329,089.

flat-wise in the groove and secured to the support in any suitable manner as, for eX- ample, by a screw G extending through the support with its shank end threaded in an aperture formed in the strap. The heating element 2 is secured to the strap by a screw 7 which is threaded to the strap or plate 5 and may extend into an aperture or clearance 8 formed in the support, the diameter of which is made larger than that of the screw so as to provide ample space for the independent expansion and contraction of the adjacent parts. The lead-in wires (not shown) may be secured to their respective straps by the screws 7 but they are preferably secured thereto by similarly arranged screws 9. The support is formed adjacent the screws 9 with apertures 10 through which the lead-in wires extend.

it is readily apparent from the foregoing, that the electrical connections provided in this unit for both the heating element and lead-in wires cannot be affected by the eX- pansion and contraction of the support or the resultant movement of the securing screw 6. In fact, this screw 6 can be entirely disengaged from the strap or plate 5 without loosening any of the electrical connections. Thus while the construction is exceedingly simple and relatively inexpensive, it completely avoids the objections noted in connection with the prior heating units of the same general type.

Having fully described my invention, I claim:

l. An electrical heating unit comprising a refractory support formed with grooves, a heating element arranged in said grooves, a conductive strap positioned in said groove and adapted to connect electrically a lead-in wire with said heating element, a screw securing said strap to said support and a pair of threaded screws independently securing said element and said lead-in wire to said strap, said screws last mentioned being spaced from the screw first mentioned and also from the support whereby the electrical connections thereby afforded are unaffected by the expansion and contraction of said support.

2. An electrical heating unit comprising a refractory support, a heating element arranged on and supported by said support, a conductive plate positioned on one side of said support adjacent one end of the heating element and adapted to connect electricall a lead-n wir@ with said heating eleen means including a screw for securing said plate to said support and a pair of screws independently securing Said element and. said lead-in wire to, said plate, said screws last mentioned threadedly engaging said plate and being spaced from said screw first men tioned to project into receiving openings in said support of greater diameter than said last mentioned screws whereby the electrical connections are unaffected by the expansion and contraction of the said support.

In testimony whereof I hereby ax my signature.

` CHARLES W. LOGAN. 

